Looking for a bulkhead solution for your 92-99 GMT400 OBS? This solution is for you these come in black with stainless hardware and feature a 1″ and .75″ hole for passing your wiring harness through. These will fit all TWS harnesses and others. Retains the original 7mm mounting screw on top and includes two additional mounting points on the sides with hardware included. TWS recommends running a bead of silicone where they attach to firewall to keep out any water. Front plate is reversible to allow different orientation of holes in pass through.